The present invention generally relates to electrophotographic copying apparatuses and more particularly, to a multiple-unit type copying apparatus having an apparatus housing divided into a plurality of units.
Conventionally, in electrophotographic copying apparatuses, it has been so arranged that an image of an original document is scanned by an optical system. At this time, light of a light source of the optical system is irradiated onto and reflected from the original document. The reflected light is led to a copying process portion in which an electrostatic latent image is formed on a surface of a photoreceptor. Then, developer is supplied to the electrostatic latent image so as to form a developer image such that the developer image is transferred onto a copy paper sheet which has been conveyed to the copying process portion from a paper feeding portion. The copy paper sheet is conveyed through a paper transport passage extending from the paper feeding portion, through the copying process portion, to a paper discharging portion. As described above, a number of devices are provided in the apparatus housing.
In the known copying apparatuses, in order to facilitate assembly and maintenance of these devices, the apparatus housing is divided into a plurality of units which are assembled with each other openably or detachably. After components have been mounted on each of the units, the units are assembled with each other, whereby replacement and maintenance of the components can be performed easily.
However, in the above described known multiple-unit type copying apparatuses, in order to drive a driving device mounted on each of the units, it is necessary to input control data to a control portion of the driving device by tapping keys of an operating portion attached to an uppermost one of the units. Therefore, in order to check a driving state of the driving devices mounted on the lower units having no driving portion, the uppermost unit should be beforehand assembled with the lower units and thus, it becomes difficult to check the driving state of the driving devices of the lower units. As a result, the known multiple-unit type copying apparatuses have such drawbacks that it is difficult to locate defective portions and it is troublesome to mount the components on each of the units.
Meanwhile, in a prior art copying apparatus, the apparatus housing is divided, at the paper transport passage, into upper and lower units. When the apparatus housing is divided into the two units as described above, mounting of the components can be performed easily. Furthermore, since the paper transport passage can be divided vertically, it becomes possible to easily remove jammed copy paper sheets from the paper transport passage. When the apparatus housing is divided, at the paper transport passage, into the two units, the paper transport passage is provided in the lower unit, while the copying process portion and the optical system are provided in the upper unit. Since each of the optical system and the copying process portion is constituted by a number of components, assembly of the upper unit is not easy. Especially, when components of the optical system are mounted on the upper unit, wires for transmitting a driving force to the light source are laid. However, since there is no ample space for laying the wires, it is troublesome to mount the components of the optical system on the upper unit.
Therefore, in Japanese Patent Application No. 257685/1986 filed on Oct. 29, 1986, the assignee assigned by the present inventors proposed a multiple-unit type copying apparatus having an apparatus housing divided into three units, in which the optical system, the copying process portion and the paper transport passage are, respectively, provided in the upper, central and lower units, respectively. In this multiple-unit type copying apparatus of the above described arrangement, since the optical system, the copying process portion and the paper transport passage can be mounted on the respective three units, productivity of the multiple-unit type copying apparatus can be raised. Especially, in assembly of the optical system, since ample space for laying the wires can be secured, the optical system can be mounted on the upper unit easily. Meanwhile, operations such as removal of jammed copy paper sheets can be performed easily by providing the units openably.
However, in this multiple-unit type copying apparatus having the apparatus housing divided into the three units, when the upper unit provided with the optical system has been opened, devices constituting the copying process portion are exposed externally. The devices constituting the copying process portion includes a rotatable photosensitive (photoreceptor) drum and a corona charger to which a high voltage is applied. Therefore, when the upper unit has been opened, an operator has access to these devices of the copying process portion. Meanwhile, at the time of adjustment of the copying apparatus after its assembly or at the time of maintenance of the copying apparatus, the serviceman or operator frequently touches these devices of the copying process portion with hands. Therefore, if adjustment or maintenance of the copying apparatus is performed in a state where electric power is supplied to the devices of the copying process portion, the serviceman or operator may be injured or the devices of the copying process portion may be damaged upon unexpected drive of the devices of the copying process portion due to erroneous operations or malfunctions of the devices of the copying process portion, thereby endangering safety of adjustment or maintenance of the copying apparatus.